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OBJECTIVES
1. Compare and contrast Aristotelian and Galilean
conceptions of vertical motion, horizontal
motion, and projectile motion;
2. Explain how Galileo inferred that objects in
vacuum fall with uniform acceleration, and that
force is not necessary to sustain horizontal
motion;
3. Explain the distinction between Newton’s 1st Law
of Motion & Galileo’s assertion that force is not
necessary to sustain horizontal motion; and
4. Cite practical applications of principles involving
motion in our day to day living.
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TERMINOLOGIES.
Vertical motion
• is referred as the movement of the object
against the gravitational pull.
• It is the motion that is perpendicular to the
straight or flat surface.
• It can also be a straight upward and
downward motion but the perfect vertical
motion does not usually pursue a straight
line path.
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TERMINOLOGIES.
Horizontal motion is defined as a projectile
motion in a horizontal plane depending
upon the force acting on it.
Projectile motion is the motion of an object thrown
(projected) into the air when, after the initial
force that launches the object, air resistance is
negligible and the only other force that object
experiences is the force of gravity.
• The object is called a projectile, and its path
is called its trajectory.
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TERMINOLOGIES.
Uniform motion refers to the motion of an
object at a constant speed in a straight line,
without any acceleration or deceleration.
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ARISTOTELIAN.
 Motion as a result of an external force:
• According to Aristotle, motion required a
continuous force to be exerted on an
object.
• Objects were believed to have a natural
tendency to be at rest, and motion was
only possible when a force was actively
applied.
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ARISTOTELIAN.
 Natural and violent motion:
• Natural motion was thought to occur for
objects seeking their "natural place" in
the universe, such as earth moving
downward and fire moving upward.
• Violent motion, on the other hand, was
believed to result from an external force
acting on an object.
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ARISTOTELIAN.
 Earth-centric view:
• Aristotle's conception of motion
was based on a geocentric view of
the universe, where the Earth was
considered the center of all
motion.
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GALILEAN.
 Inertia and independent motion:
• Galileo introduced the concept of
inertia, which stated that an object at
rest tends to stay at rest, and an object
in motion tends to stay in motion with
the same speed and direction unless
acted upon by an external force.
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Inertia: Galileo's concept of inertia states that an
object at rest tends to stay at rest, and an
object in motion tends to stay in motion with
the same speed and direction unless acted
upon by an external force.
 In other words, inertia is the property of matter
that resists changes in its state of motion.
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• Galileo's insight challenged the prevailing
Aristotelian view that a continuous force was
required to keep an object in motion.
• He observed that objects would continue
moving on their own, even in the absence of
an applied force, as long as no external force
acted upon them.
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GALILEAN.
 Uniformity and relativity of motion:
• Galileo's principle of relativity suggested
that the laws of physics are the same in all
inertial reference frames.
• He argued that the fundamental laws of
motion apply uniformly to all objects in
motion, regardless of their specific
conditions or locations.
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GALILEAN.
 Observational and experimental approach:
• Galileo supported his ideas with empirical
evidence gathered through experiments and
observations.
• He challenged traditional beliefs by conducting
experiments, such as his work with inclined
planes, which demonstrated that objects of
different masses fall at the same rate in the
absence of air resistance.
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GALILEAN
ARISTOTELIAN
MOTION AS A
RESULT OF AN
EXTERNAL FORCE
NATURAL AND
VIOLENT MOTION
EARTH CENTRIC
VIEW
INERTIA AND
INDEPENDENT
MOTION
SOURCE OF MOTION
TYPES OF MOTION
VIEW OF THE
UNIVERSE
EMPERICAL
EVIDENCE
UNIFORMITY AND
RELATIVITY OF
MOTION
OBSERVATIONAL
AND
EXPERIMENTAL
APPROACH
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Galileo's experiments led to the
rejection of Aristotle's view
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Inclined Plane Experiment:
•
•
Galileo conducted experiments with
inclined planes to study the motion of
objects rolling or sliding down a
sloping surface.
By adjusting the angle of the incline
and measuring the time taken for
objects to reach the bottom, Galileo
made several
key observations that contradicted
Aristotle's view:
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a. Uniform Acceleration:
Galileo observed that objects rolling
down the inclined plane exhibited a
uniform acceleration.
b. Independence of Mass:
Galileo discovered that objects of
different masses, when released from
the same height on the inclined plane,
reached the bottom simultaneously.
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c. Conservation of Energy:
Galileo's experiments also revealed
that the potential energy of an object
at the top of the inclined plane
converted into kinetic energy as it
moved downward.
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• Galileo's experiments, including the inclined
plane experiment, directly contradicted
Aristotle's view of motion.
• The uniform acceleration, independence of
mass, and conservation of energy observed
in Galileo's experiments provided
compelling evidence against Aristotle's
claims.
• Galileo's empirical approach, publication of
his findings, and the subsequent impact on
the scientific community led to the rejection
of Aristotle's view and marked a significant
shift in our understanding of motion.
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